Indicating fuse plug



Jan. 16, 1934. -w H INDER 1,944,145

I INDICATING FUSE PLUG Filed Sept. 26, 1933 INVEQJTOR ATTORNEY Patented Jan. 16, 1934 UNITED STATES INDICATING FUSE PLUG William H. Ginder, Haddonfiel'd, N. J., assignor of fifty-one per cent to Isaac C. Shalkop, Philadelphia, Pa.

Application September 26, 1933 Serial No. 690,974

3 Claims.

This invention relates to indicating fuse plugs. The difliculty in locating a ruptured or blown fuse, in a bank of unblown fuses in a fuse box or the like, is well known. There have been many efforts made to provide indicating fuses of various types, and of varying degrees of complexity, but so far as known they have almost all failed of commercial success. The failures may in large measure be accounted for by uncertain- 1 ty of signals, by high manufacturing and distributing costs, and by failure to meet safety requirements.

It is among the objects of this invention; to provide an indicating fuse plug which obviates the difficulties of prior art devices; to provide a fuse plug of standard construction with a positive signal or indicating means of low manufacturing costs; to provide a fuse plug making a permanent record of the rupture of the fusible element; to provide a fuse plug involving stationary parts as the signalling and indicating device; to provide an indicating fuse plug that indicates the condition of the fuse regardless of the flow of current relative to the fuse; and generally to improve the art of fuse plugs. Many other objects and advantages will become more apparent as the description proceeds.

In the accompanying drawing:

Fig. 1 represents a vertical section through the assembled indicating fuse plug according to one form of the invention,

Fig. 2 represents a plan view of the plug prior to the blowing or rupture of the fuse,

Fig. 3 represents a similar plan after the rupture of the fuse and the obliteration of the symbol of correct order on the exposed face of the plug,

Fig. 4 represents a transverse section through the plug taken on line 44 of Fig. 1,

Fig. 5 represents a plan of the signal element of the fuse according to one form thereof, and

Figs. through modified forms of the signal element usable with the fuse.

In its essence the indicating fuse plug of this invention comprises a standard fuse plug with the conventional insulating housing having the external brass threaded sleeve, the axial terminal, the conventional fusible link secured electrically to the threads and to the axial terminal, the conventional closure cap having the axial opening through which the mica window can be seen held against the upper end of the insulating housing, modified merely by inserting a 6 and 7 represent vertical sections.

cupped combustible element under the mica with, preferably, a flashing compound in position to be ignited by the heat of fusion of the link and in turn to initiate combustion of the cupped element to char cr scorch same to make a visible indication on the element, which is readily visible through the mica.

Referring to Fig. 1, a porcelain housing 10 of conventional construction and insulating properties, has the axial terminal 11 and threaded metallic sleeve 12 forming terminals for the fusible link 13. The link preferably has a substantially plane portion 14 disposed toward the open end of the housing although spaced inwardly from the plane of such opening and usually and preferably has a lateral notch or recess 15 in such position as to cause the blow or rupture of the fuse incident to overload in the circuit to take place in the plane 14 beneath the mica window 20. The standard fuse used in this invention includes a metallic sleeve or flanged ferrule 16 having an axial opening 17, and having the flange 18 in position to engage and hold in place the mica or similar window element 20. The foregoing represent the items of a standard conventional fuse such as are available in either assembled or disassembled relation at very low prices. It will be appreciated that the lower the parts cost, and the fewer special parts that need be provided, the cheaper the production of the new article from both the material and labor standpoint.

As shown in Fig. 5, in the preferred form, there is provided a cupped or dished combustible element 19 comprised of an outer plane periphery 21, which may be crimped or otherwise treated as at radial lines 22, as to maintain the plane edge 21, while having the axial depression or concavity 23. The element 19 is preferably formed of a treated fibrous material, such as paper, impregnated with saltpetre or the like, and when dried and mounted in the end of the housing 10, as shown in Fig. 1, has the convex surface of the axial depression extended downwardly close to or axially in contact with the planar portion 14 of the fusible link. It will be quite evident that in the assembly of the complete fuses the insertion of the element 19 under the mica window 29 with the substantially planar edge 21 against the end of housing 10 is an extremely simple and obvious operation. It will be clear that the cupped element might be one that is of itself so highly combustible that the heat of fusion of the link 13 will ignite same. It is a feature of the invention that a symbol of safety or of correct or good order, such as the letters 0. K3, shown at 24, may be imprinted or otherwise form-ed on the mica or outer side and in the concavity of the element 19. It will be clear that combustion of the element 19 upon fusion of the fuse 13 will so char or scorch the element 19 to a degree at least sufficient to obliterate the symbol 24, and so clearly and completely indicate to the operator that the fuse is of no further usefulness and should be replaced.

In the usual case of the element 19, it will be found that the heat of fusion of link 13 is insufficient to ignite the element 19. To prevent failure of the indication on this ground it is preferred to use an igniter or flasher as a sort of combustion booster. This may take the form of a compound of explosive materials, such for instance as gun powder, or flashlight powder or the like in a binder, such as to cause it to remain in position until used. Thus, in one form, the manufacturer of the indicating fuse will cause a drop of the igniting or flashing substance and its binder, such as globule 25, to be placed adhesively upon the planar portion 14 of the fuse link 13, at its weak point 15, and the element 19 will be disposed so close thereto as to be ignited when the globule is consumed.

In certain other forms of the invention, of possibly even greater simplicity and economy, as shown in Figs. 6 and '7, the globule of flashing material 25 will be attached directly to the under side or convexity of the combustible element 19. Thus in Fig. 6 the element 19 of treated paper carries the flasher 25 directly. In Fig. 7, the combustible element comprises preferably a stamped or molded shell 26, of combustible material such as of celluloid or other cellulose derivative, having the pocket 27 stamped therein and in which the flasher 25 is adhesively disposed.

It is not necessary that the flasher directly and actually contact the fusible link, although generally the closer the better, and it is not necessary that the dished or depressed or cupped element extend inwardly to actual contact with the flasher or with the fuse link, although, again, the closer the better, generally speaking.

Among other pronounced advantages of the invention are the facts that the inwardly extending combustible material obviates all necessity for changing the construction of fuses from the conventional to secure the desired result, it prevents the necessity for building additional current conductors and shunt circuits in order to reach the indicating area and surface, and, finally, it enables the combustible element at its point of combustion to have air on both sides, both toward the mica window, and toward the axial terminal, to facilitate combustion, and insure a complete indication. This is of importance.

I claim:

1. In indicating fuses, an indicating element cmprising a disc, the central part at least of which is of combustible material, the disc having its periphery in a substantial plane and the central portion depressed concavely out of said plane, said disc arranged to seat directly upon the mouth end of a plug fuse housing and to receive a transparent disc on its periphery and to form relative to said transparent disc an air pocket, said concavity arranged to extend inwardly of the mouth of the plug fuse toward a fuse link in the housing, and arranged to ignite upon rupture of the fuse link.

2. In indicating fuses, an indicating elementcomprising a disc, the central part at least of which is of combustible material, the disc having its periphery in a substantial plane and the central portion depressed concavely out of said plane, said disc arranged to seat directly upon the mouth end of a plug fuse housing and to receive a transparent disc on its periphery and to form relative to said transparent disc an air pocket, said concavity arranged to extend inwardly of the mouth of the plug fuse toward a. fuse link in the housing, and a flashing element attached to the indicating element and exposed on the convex face of the element and arranged to ignite and initiate combustion of the combustible material of the indicating element.

3. In indicating fuses in combination, a fuse plug housing having an open mouth, a fuse link inwardly of the mouth of the housing, an indicating element comprising a disc the central portion at least of which is of combustible material, the outer periphery of the disc being in a substantial plane arranged to seat upon the mouth of the plug housing, the disc having an inwardly depressed concavity extending toward the fuse link, a planar disc of transparent insulating material seated upon the substantially planar periphery of the combustible disc and forming with the depression an air pocket, and a sleeve engaging the transparent disc and holding both said discs on the housing.

WILLIAM H. GINDER. 

